Knurling device



Oct. 6, 1953 4 Sheets-Sheet 1 Filed Aug. 24, 1949 a w; & 7 ww m w 6 a z y 4 MI// Q? 6 5 .w L a M N l JAM M C. F. JONES KNURLING DEVICE Oct. 6, 1953 4 Sheets-Sheet 2 Filed Aug. 24, 1949 INVENTOR. Cv'ywlifones, BY @4484, M,

1953 c. F. JONES 2,654,275

KNURLING DEVICE Filed Aug. 24, 1949 4 Sheets-Sheet 3 IIIIIUIIIHIH ill/0 lei? IN V EN TOR.

, Cr zywlzfwzea,

Oct. 6, 1953 c. F. JONES 2,654,275

KNURLING DEVICE Filed Aug. 24, 1949 4 Sheets-Sheet 4 INVENTOR. I

Cerggz'z/ffanea BY 50%,

Patented Get. 6, 1953 UNITED sures PATENT orFrcr.

KNURLING DEVIC Cernyw F. Jones, Economy, 1116., assignor to Perfect Circle Corporation, Hagerstown, 1nd,, a corporation of Indiana Application A gust-24, 1949, Serial No. 112,048

11 Claims. 1

This invention relates generally'to a knurling device for knurling the peripheral surface of a cylindrical object and more particularly to a device for knurling'predetermined areas on the peripheral surface of a hollow cylindrical article such as a piston for aninternal combustion engine.

With continued operation of an internal combustion engine, the pistons and cylinders tend to wear or become distorted with the result that the normal fit of the pistons within the cylinders is lost. This condition is often characterized by piston slap and other evidence of excessive looseness. The lack of proper fit between the piston and the cylinder is objectionable since it impairs engine efiiciency and has an adverse effect on the economy of operation.

Various means for correcting this condition have been employed, one method involving the expansion of the outer wall or skirt portion of the piston sufficiently to reestablish the normal fit between piston and cylinder. Such expansion may be accomplished, for example, by knurling the outer surface of the piston to form roughened areas on the thrust faces thereof'having an interrupted surface comprising projecting portions with intervening depressions. During knurling, the metal is extruded or swaged to a sufficient extent so that the projections'formedon the piston surface extend outwardly to the desired increased size whereby the 'proper'fit between the piston and the cylinder is realized.

Although during knurling of a-piston the work may be supported .or stabilized .by hand of the operator, it is generally desirable to provide the ,knurling device with a suitable work-supporting member or structurewhich resultsin'more effective stabilization of the piston during knurling and also frees both hands of the operator for manipulation of the knurling mechanism proper.

Because the normal contour of a piston is slightly oval or out-of-round, it is necessarythat such a work support bedesigned topermit a limited degree of relative movement between the piston and the work supportin order tto-compensate-wfor the varying piston diameter. -In qfidditiQH, the knurling mechanism preferably comprises an anvil member or other supporting-meansadapted to engage and support the piston internailywhile a knurling element engages the exterior ofthe piston under pressure. However, the interior surface of the skirt portion of .a pistonisusually quite uneven in the area between the wrist pin bosses because of various protuberances and surface irregularities such as reinforcing ribs,

partial machining of the interior surface, and general surface roughness characteristic of cast articles. Thus, the problem is presented of providing a knurling device which will readily accommodate the variations in piston wall thickness while at the same time avoiding any substantial change in knurling pressure against the outer surface of the-piston.

Accordingly, one object of my invention is to provide a novel device for knurling the exterior surfaces of pistons which readily accommodates variations in piston wall thickness while maintaining a substantially constant knurling pressure.

Another object of my invention is to provide a novel device for knurling the exterior surfaces of pistons inwhich a supporting member engages the interior of the piston, a knurling member engages the exterior of the piston, and the spacing between said membersis permitted'to vary automatically to accommodate protuberances and other irregularities on the interior surface of the piston,

An additional object of the invention is to provide a simple hand-operated device for knurling the exterior surface of a piston in combination piston.

A still further object of the invention is to provide a manually operable device forknurling the exteriorsurfaces of pistons which is simple and rapidv in operation 'and which can be manipulated 'by'a op rat r w th marked convenience and witho t e ces v e r ion.

Other objects and advantages of the invention ill become apparent frornthe subsequent detailed description of the invention and the .accompanying drawings; in which:

Fig. 1 is a-vertical sectional view of a knurling devicecomprising one specific embodiment of my invention and'taken' substantially along the line 1-1 of Fig; 4;

Fig. -2 is a top plan view of the device shown -inFig.-1;

1 Fig. 3 is apvertical sectional-view taken alon the line 3-3 of Fig. 2; g

Fig. 9 is an end view of the device-when viewed from the right in Fig. 5.

The knurling device comprising the present invention is provided with a pairof cooperating anvil and knurling elements, the anvil element being arranged to support the piston internally while the knurling element bears against the outer surface of the piston. The knurling element may be in the form of a small roller mounted for rotary reciprocating or oscillating movement, the roller being applied to the outer surface of the piston in rolling relation therewith so that the resultant area knurled in one application of the tool comprises a band having a width equal to the width of the roller. Alternatively, the knurling element may also be in the form of a flat bar or elongated member adapted to be reciprocated rectilinearly while in knurling engagement with the exterior of the piston whereby to produce a similar knurled band. In either case the knurling element is usually relatively narrow and. traverses the piston circumferentially so that a plurality of such knurled bands are required to cover a desired area longitudinally of the piston. The knurled bands may, of course, be disposed in continuous abutting relation to one another or they may be slightly spaced from each other longitudinally of the piston.

With a piston for an internal combustion engine, it is necessary to knurl only the thrust faces of the piston skirt, i. e., those portions which are subjected to lateral thrust against the cylinder wall due to the position of the connecting rod. Thus, the knurling operation may be restricted to the portions of the piston skirt lying intermediate the wrist-pin holes on opposite sides of the piston. The knurled area preferably starts immediately below the ring grooves at the upper end of the piston and may extend axially or longitudinally for the full length of the piston skirt. If desired, the knurled band at the extreme outer end of the skirt may be spaced differently from the remaining bands in order to position the outermost band as close as possible to the lower edge of the piston.

In addition to effecting expansion of the piston metal by extrusion thereof, in the manner hereinbefore described, whereby to reestablish a proper fit between the piston and the cylinder, the knurled surface obtained by my invention also offers other important advantages. For example, it has been found that better performance is obtained in a reciprocating piston and cylinder, or other like construction, if one of the two surfaces is of an interrupted nature comprising projecting portions with interventing depressions, such as may be provided by knurling. A surface of this character has been found to run cooler than an absolutely smooth surface for pistons as well as other cylindrical objects adapted to reciprocate within a bore. Another advantage inherent in knurling the surfaces of pistons and like articles is found in the improved wearing qualities of the knurled surface result ing from the hardening effects of cold working the metal. Moreover, the interrupted surface afforded by knurling provides a series of pockets or reservoirs which serve to retain lubricating oil and thereby maintain a continuous supply of lubricant at the surface-contacting areas.

It will be apparent that, in addition to the obvious utility of knurling old or worn pistons in order to expand the same, knurling may also be resorted to in the case of new pistons or original assemblies of pistons within their cylinders in order to attain the other advantages mentioned above. While the knurling device comprising the present invention is designed primarily for knurling pistons, the invention is not limited in this manner but embraces the knurling of the peripheral surfaces of hollow cylindrical articles generally.

The term knurling as used throughout the specification and the claims is not limited to the ordinary form of knurling involving grooves arranged in a cross-cross pattern, but rather is used in a broad sense to include any surface formation involving alternate depressed and raised portions regardless of whether one or the other or both of said portions are continuous throughout the area having such formation. Thus, the term includes not only the criss-cross pattern but also a pattern formed by parallel grooves or by isolated indentations resulting in connected raised portions.

' As hereinbefore mentioned, an important object of my invention is to provide a knurling device for pistons which is designed to accommodate varying piston wall thicknesses due to internal protuberances or surface irregularities while at the same time avoiding substantial changes in knurling pressure and eliminating the need for manually adjusting or regulating the device during a knurling operation. I accomplish this end broadly by providing a. knurling member and a cooperating anvil member pivotally or shiftably mounted for movement toward and away from the knurling member, in combination with a spring means for yieldingly urging the anvil member toward the knurling member. The yieldable urging of the one member toward the other permits a variation in spacing between the members upon contact of the anvil member with protuberances on the interior surface of the piston skirt while the knurling member bears with substantially constant pressure against the exterior surface of the skirt.

Form shown in Figs. 1-4

Referring now to Figs. 1 to 4 of the drawings, which show by way of illustration one specific embodiment of my invention, the device comprises a generally rectangular body member or base In having depending end walls I l and front and rear walls l2 and 13, respectively, for supporting the device on a work bench or other horizontal work surface. At one end of the base It! is a raised bed I4 comprising a machined worksupporting surface which extends transversely of the device. A pair of stabilizing wings $5 of semi-rigid or resilient construction are slidably mounted on the bed M by means of a pair of upright studs 16 which extend through the base portions of the wings l5. Retaining nuts, indicated at I! (Fig. 1) are attached to the lower ends of the studs l6 and are slidably retained in an elongated T-shaped slot 18 in the bed 14. The studs (6 are threaded at their upper ends into a pair of clamping nuts III for adjustably clamping the wings I in desired spaced relation on the bed I4. As shown in broken lines in Figs. 1, 3 and 4, a

piston 20 may be disposed above the bed I4 and may be stabilized against twisting movement during knurling by engagement of the wings I5 at opposite sides of the piston. Thus, by adjustment of the studs I6 and the nuts I9, the wings I5 may be positioned at any desired spacing de- In this embodiment of the invention an elongated bar-type knurling element is utilized. To this end, an elongated groove 2I is provided adjacent the inner edge of the bed I4 and parallel to the T-shaped slot I8. Slidably disposed within the groove 2| is an elongated knurl carrier or slide 22 having a rack or gear teeth 23 (Fig. 3) at its bottom side. The elongated bar-type or flat knurling element, indicated at '24, is detachably secured in the knurl carrier '22 by means of a pair of set screws 25 having pointed inner ends which are received within offset notches or cavities 25 in the ends of the knurling element 24 whereby the knurl 24 is held tightly against the slide 22 with the upper or work face of the knurled projecting slightly above the surface of the bed I4 (Figs. 1 and 3). It will be understood that the work face of the knurling element 24 is formed with a roughened knurling surface, of the character hereinbefore described, for contacting and knurling the outer periphery of the piston 29.

For driving the knurl 24, an elongated drive shaft 2'! is journaled at one end in a bore 28 (Fig. 1) provided in the base II] and extends at its opposite end through an end wall II and is journaled therein, as at 29. A set screw 30 is provided for engaging a groove in the shaft 21 to prevent endwise movement thereof. A pinion 3| is formed at the inner end of the shaft 21 and meshes with the rack 23. A hand crank 32 extends through the outer end of the shaft 21 for manually driving the knurl 24 and is secured in adjusted position by means of a set screw 2-3. Upon rotation of the hand crank 32 in alternate directions, reciprocating sliding movement in a rectilinear path is imparted to the knurling element 24 whereby to produce a knurled band on the outer periphery of the piston 20.

For controlling and limiting the length of the knurl tracks on the piston 20, a pair of stops are provided for limiting the rectilinear movement of the knurling element 24. To this end, a pair of supports 34 (Fig. 3) are secured to the front and rear walls I2 and I3 by means of a plurality of screws 36, and a pair of elongated screws or adjustable stop members 31 are threaded through the upper portions of the supports 34 and project into the opposite ends of the groove 2 I. Each of the stop screws 31 is provided with a locking nut 38 for fixing the adjusted position of the stop members, the opposite ends of the knurl carrier 22 being adapted to engage or abut the inner ends of the screws 3! whereby to limit the extent of reciprocating sliding movement of the knurl carrier 22 and the knurling element 24.

To provide an anvil support, a bell crank, indicated generally at'39 (Fig. 4), having a generally horizontal short arm AI and a depending long arm'42, is pivotally supported on the base II] by means of a fulcrum pin orpivot-shaft 43 journaled between a pair of upright lugs or ears 44 extending upwardly from the base II]. An elongated anvil-supporting arm 46 is rigidly attached, as by a pair of screws 41, to the end of the short arm 4| of the bell crank 39 and extends parallel to the drive shaft 2-1 toward the open end of the piston 20. The outermost end of the arm 46 is provided with a pair of spaced projections between which is mounted for free rolling movement an anvil member in the form of a hard smooth-surfaced roller 48 having approximately the same width as the knurling element 24. The anvil roller 48 is carried on a pin 49 and is positioned in radial alignment with respect to the knurli'ng element 24 for engaging the inner periphery of the piston 20 as the knurlin'g element traverses the outer surface of the piston.

The long arm 42 of the bell crank 39 eiiten'ds downwardly through a slot or opening 5! in the base I0 and is bifurcated at its lower end, as "at 52 (Fig. 4), a swivel in the form of a pin or shaft 53 being journaled through the bifurcated portions thereof. An elongated spring-loading device, indicated generally at 54, extends horizontally between the walls I2 and I3 of the base Id and coacts with the bell 'cra'nk39 for applying adjustable yielding pressure against the leg 42 whereby the anvil roller 48 is normally urged toward the knurling element '24. The springloading device 54 comprises an elongated screw 55 having terminally threaded portions and'extending longitudinally through a transverse aperture 5% in the shaft 53 between the bifurcated end portions 52 of the leg 42 and projecting through an opening 51 in the rear wall I3. The forward end of the screw 55 extends through an enlarged concentric bore 58 in the front wall l2 of the base It. Thescrew 55 is also threaded through a swivel in the form "of a pin or shaft 5| rotatably supported at one end in "a boss 59 formed on the inner face of the front wall I2 and at its other end in the adjacent end wall I I. Encircling the screw 55 is -a helical spring '62 adapted to apply yielding pressure against the shaft 53 through athrust collar 63. A spring load adjusting nut 64 is threaded at the "rear end of the screw 55 and bears against the'oppo site end of the spring'62 through a similarthrust collar 65. Another thrust collar, comprising a loosely mounted thrust washer 61 and a thrust washer 58 rigidly secured to the screw 55, is disposed 0n the opposite side of the shaft 53 for engaging the latter and urging the anvil roller 38 to released position, ashereinafter describedin detail. A handle 59 is attached to the forward end of the screw 55 for rotating the same.

By adjusting the nut 54, the tension of the spring 62 can be regulated to control the spring pressure exerted on'the leg 42 of the bell-crank 39 and thereby regulating the knurling pressure, i, e. the pressure under which the skirt portion of the piston 25 is pressed against the knurling element 24 by means of the internal anvil roller 48. A jam or look nut I5 is carried on thescrew 55 beyond the adjusting nut 64 for locking the latter in place after'the spring tension has been adjusted to any desired extent.

The operation of the spring loading device 54; is as follows: In the position shown in Fig. 4, the screw 55 has been moved forwardly by its threaded connection with the shaft '6I so that'a slight clearance, indicated at II, is established between the thrust washer 61 and the shaft 53. Thus, the full pressure of the spring 62 is brought to bear on the shaft 53 thereby urging the bell crank 39 in a clockwise direction, as viewed in Fig. 4, and causing the anvil roller 58 to be pressed toward the knurling element 24 with the skirt portion of the piston 20 being clamped therebetween. As described above, the knurling pressure may be controlled by adjusting the nut 64 to regulate the tension of the spring 62.

By means of the handle 69, the screw 55 may be screwed inwardly of the device at its threaded connection with the shaft 6! until the thrust washer 61 abuts the shaft 53 thereby rendering the sprin load ineffective as the clearance H is taken up. At this point, continued inward movement of the screw 55 causes the leg 42 to be rocked rearwardly of the device and the anvil roller 48 to be moved away from the interior surface of the piston 29 to released position as the bell crank 39 rotates in a counterclockwise direction about the fulcrum pin 43, as viewed in Fig. 4. With the roller 48 and the knurling element 25 in spaced relation, the skirt of the piston 20 may be withdrawn or inserted to the desired extent. As the leg 42 swings rearwardly of the device in an arcuate path during movement of the anvil roller 48 to released position, the rear end of the screw 55 swings slightly in a downward direction, as viewed in Fig. 4. To accommodate this pivotal movement of the screw 55, the swivel shafts BI and 53 rotate freely in their respective supporting structures, the bifurcated end 52 of the leg 42 and the enlarged bore 58 in the front wall l2 providing sufficient clearance to permit the screw 55 to assume the necessary angular position.

During the inward movement of the screw 55, the tension setting of the spring 62 is not materially disturbed since the spring tension is determined by the relative position of the adjusting nut 64 on the screw 55. Inward movement of the screw 55 from the position shown in Fig. 4 until the clearance H is taken up will result in a very slight decrease in the spring tension setting equivalent to the extent of the clearance H, but this change is of no practical consequence. Thus, it will be seen that the anvil roller 48 can be backed away from the skirt portion of the piston 25 without unloading the spring 82 or otherwise changing the spring tension setting.

To return the device to knurling position, the handle 69 is operated in reverse fashion whereby the screw 55 is moved forwardly of the device through the shaft 6! and the tension of the spring 52 acting on the shaft 53 pivots the bell crank 39 to swing the anvil roller 48 into contact with the inner surface of the piston 20 with sufiicient pressure to sink the ridges on the knurling element 24 into the outer surface of the piston skirt. Further movement of the bell crank 35 and its leg 42 is prevented, and forward movement of the screw 55 is continued until the slight clearance H is reestablished between the shaft 53 and the thrust washer =51. Thus, the spring 62 is returned substantially to its original tension and the full spring load is again imposed on the shaft 53. Once the clearance H is obtained, further operation of the handle 69 is unnecessary since the establishment of the slightest clearance at this point permits the full spring tension, as determined by the setting of the nut 64, to be applied against the shaft '53.

In knurling a piston with the device shown in Figs. 1 to 4, the piston 20 is first positioned on 8 the bed [4 with the skirt portion thereof extending between the anvil roller 48 and the knurling element 24 to the desired extent while the anvil supporting arm 46 is in released position. The stabilizing wings 55 are then slid into contact with the exterior of the piston and are secured in position by means of the studs l5 and the clamping nuts I9. Upon adjustment of the nut 64 to obtain the desired tension in the spring 52 and upon backing oif of the screw 55 by means of the handle 69 to return the arm 45 to operating position, the desired knurling operation may then be carried out by adjusting the stop screws 31 to obtain a knurl track of desired length and then rotating the hand crank 32 in alternate directions to effect reciprocating rectilinear movement of the knurl carrier 22 and the knurling element 24.

Rotation of the hand crank 32 results in relative movement between the knurling element 2 and the piston 28 circumferentially of the latter and, because the skirt portion of the piston 26 is clamped between the anvil roller 48 and the knurling element 25, reciprocating sliding movement of the knurling element 24 also causes simultaneous rotation of the piston 20 on its axis whereby to form an arcuate knurled band on the outer periphery of the skirt, as hereinbefore mentioned.

During knurling, the piston 26 is held squarely against the face of the knurling element 2-; by means of the clamping action of the anvil roller 43 forcing the piston skirt against the knurl. The semi-rigid stabilizing wings 15, which are clamped in position on the bed 14 by means of the studs l5 and the nuts 19, engage the sides of the piston 28 to stabilize the piston against twisting movement in a horizontal plane. The stabilizing wings 45, while adapted to resist any tendency toward twisting movement of the piston, are also sufficiently flexible or resilient to accommodate slight variations in the eifective diameter of the piston 20 as a result of its normal out-of-round contour. In other words, as the piston 20 rotates on its axis while firmly clamped between the anvil roller a; and the knurling element 24, the stabilizing wings l 5 will flex inwardly and outward 1y to a slight extent as they ride on the periphery of the piston whereby to accommodate variations in piston diameter while at the same time effectively stabilizing the piston against twisting movement longitudinally thereof.

During the course of a knurling operation, if the anvil roller 58 encounters internal protuberances or other surface irregularities on the in terior of the piston skirt, it will be seen that yielding application of the anvil roller 48, by the spring loading device 55, against the inner surface of the piston skirt permits the roller 38 to be forced away from the protuberance, the bell crank 39 rocking in a counterclockwise direction about the fulcrum pin 43, as viewed in Fig. 4, and the vertical leg 32 being forced rearwardly of the device against the action of the spring "62. The slight compression of the spring 62 resulting from such rocking movement will have no significant effect on the pressure with which the skirt portion of the piston 29 is clamped between the anvil roller 48 and the knurling element 24. Thus, my device provides substantially Constant knurling pressure, as predetermined by the setting of the ad- J ng nut 64 and the lock nut 19, even whe t spacing between the roller 48 and th knurl g4 vanes as the roller passes over surface irregularities on the interior of the piston skirt.

-form ofa roller having geared operating connections with a hand lever, In additionitheanv-il supporting arm is pivotally mounted directly on the base structure, thereby eliminating the bell crank arrangement show also a modified is utilized.

In this form of the invention an elongated body member or base structure 8! slJt'Q ided with a narrow upright work support 82 at one i ee- .1 te nd form of; the spring loading device end thereof. An elongated bar 83 extends transversely through the work support 81 and is secured in position therein by means of a set screw cs (Fig. 6).

s tabl m uhted a @P ends of the bar 83 are apiair or socket members 86 each carrying an upright semi-rigid sta izing wing 82* which is adapted to engage theiout er periphery of a piston as indicated'by broken ne it, e h t h e n ehp it O e work support 62. The socket members 86 are slidable along the bar to aceommodate pistens. in ia er n a secur d n e ed eeee d l eh e he be? t? b ans of e a r of mpin e r we 5 extendin h gh the eeeh ihte en a emen h e hei f wett n flattened ter iehe I at Qnne e hdse t eber t A kh r i s rol er 2 whi h. nheie ts upward y sl ghtly ab the 11. ef' h' were uh e t ist s se ured by a screw'ee t he e d e it sh r sha 8 which is 1 hr: e ed. n e. ee ihs tleeh 5 extendin uii a l n t; the ase I. an rigidly .s et ed'th retoyas b a ha r e s rews. Ft 6 Gear tee h. indifcated at 97 and comprising a pini are proyided h the the t 4 adja ent the hu i h an ehh ar flange team d. to ehsage the d face. o h eer h bl ck .95. teret ni h shatt against ehdw se m ement.- test set r in m s e n a ement h' he tea which is also journaled in the bearing block at the lower portion thereof below the shaft 94. The shaft I 3I is keyed to one endof an clone s ted. dr v af I i u aled a os r latter whereby to regulate track on the piston 88. I I

To provide an n il sup ort, a. hl h I .8 pire e y m u d. at the end thereof on a s a or pin I93 journaled on the base 8| between. a

he len th o the kne l pair f up ht ear r l sts Ila. Secured to the bloel; I68 by means of a pair of screws. 1 H and extending longitudinally therefrom is an. elon.-. gated anvilesupporting arm II 2 carrying an anvil roller I I3 at its opposite end inradial' alignment above the knurling roller ilhthe'roller I [3 hav-v ing substantially the samew-idth and diameter as the roller 92, A spring loading device, indie- I rling roller 92, the! the p te nd he shaf 9!! s f med teet is mou t n th nd o ee it t Y oscillating or back and forth movement of the I the form of a pin or shaft H9 journaled in the base structure 81. and extending transversely of the bore IIfi. A helical spring l2l encircles the screw HE and bears at one end against the outer face of a oup=like bridge member or thrust member. I22 whichseats on the upper side of the block I08 and the arm H2. The spring I2I is retained at its other end by atension adjusting nut I23 and a thrust collar comprising a plurality of thrust washers. A. look nut or jam nut I28 is also provided adjacent the nut I23 for locking the latter in place in order to maintain any desired tension setting of the spring I2I. A thrust collar I2! is rigidly mounted on the screw 1 I6 and is received within the member I22, the diameter of the thrust collar I27 being less than the internal diameter of the member I22. A handle I28 is provided at the outer end of the serew- H6 for effecting rotation of the latter. As viewed in Fig. 5; the screw HE is screwed downwardly through its threaded connection with the swivel II 9 a suffi-cient amount so that a slight clearance, indicated at I29, exists between the thrust collar I 21 and the under side of the thrust member I22. In this position the full load of the spring- 121 'is'imposed on the arm I I2 thereby yieldingly urging the anvil roller II3 toward the knur'ling roller 92,the piston 83 having its skirt portionemmpeo between the'rollers I I3 and 92;. To reiease the'lgnurling pressure the screw I I 6 is screwed outwardly by means or the handle I28. "As-the clearance I253 is 'taken up, the thrust collar IZ'I en'ga'ges the member I22, and upon continued outward movement or the screw I IQ, the member I22 is lifted upwardly from the block I08 and the arm II2. During backing-off of the screw a h ee Sh in "It! d e es d in a c i 1 in the y etteeture 8". an a n a ns h bottom face of the block I98 causes the latter t9 pi t upward ahe t e fu cru pin 9 the b s n in he a m II u a d an di e i' e ihe e an i o le I I rom the interior s r a he meter; t8 As t e rm H2 i h me ee te eleas d nq ie e screw I t r e sl ghtl t th ti ht as w d inns. s h swivel! I3 rotates to accommodate the angular unwardly pivoted position of the arm Hz. The enlarged bore II'I the, block 18 and the bore H8 in the base structure 8| are of sutlicient size to provide the necessary clearance required to accommodate the pivotal movement of the 'ee eWII i A5 l 't de ie se n h eprin 5 F 1 t it will be e V g load of the device .I :14 can thu he releas d from the a I I 2 w o ha n he ee he' e he t n i n ad u n m he and without. otherwise materially altering the Sp n e sur Te 'retu' h he spr n n device I I e knurling position, the screw I I6 is screwed down h rdl ther hr tereih the arm. II? d whwere the hiee treei h se ies It an w en the anvil te ler It eeh e the in e ior f. the ehirtrert eh at the uiete 8.8 the. crew 6 is 11 screwed inwardly a slight distance farther until the clearance I29 is reestablished and the full spring load is thereby brought to bear on the arm H2 whereby to sink the ridges of the knurling roller 92 into the metal of the piston skirt.

During use of the knurling device, the piston 88 rests on the work support 82 while the skirt portion of the piston is inserted between the rollers H3 and 92 to the desired extent with the anvil supporting arm H2 in released position. When the spring loading device H4 is manipulated to return the arm H2 and roller H3 to knurling position under a predetermined spring pressure as regulated by the adjusting nut I23, the knurling roller 92 is then rotated by oscillating movement of the hand lever I03 back and forth between the stop members I06. As in the previously described embodiment of my invention, the piston is stabilized during knurling by the clamping action of the rollers H3 and 92 and also by the resilient pressure of the stabilizing wings 87 which resist any tendency toward twisting of the piston during knurling while at the same time flexing inwardly and outwardly to accommodate slight variations in the diameter of the piston 88 as the latter rotates on its axis. As the anvil roller H3 encounters protruding conformations on the inner surface of the piston skirt, the roller H3 is forced away from the roller 92 without substantially changing the knurling pressure.

An important advantage of this embodiment of my invention is in the speed and ease of manipulation of the manual means for driving the knurling roller. In general, the stroke on the hand lever I03 may conveniently be less than 90 for piston diameters up to 5 /2 or 6 inches and, as a result, the knurling mechanism may be manipulated quite rapidly and with minimum fatigue and marked convenience to the operator. In addition, the location of the knurling roller 82 and the general construction of the device in the knurling area are such that ample illumination and space are provided for micrometer measurements and the like.

Another important advantage of the present form of the invention resides in the arrangement of the stop means for regulating the length of the hand lever stroke and thereby the extent of the knurl track on the piston. The knurl tracks on the piston may be conveniently centered by marking a line or other indicia on the inner end of the piston skirt 90 from one of the wrist pin holes and then lining this mark up with a groove, such as shown at 133 in Fig. '7, provided at the top of the knurl shaft 94. By thus aligning the knurling area of the piston with the knurl shaft, the hand lever I93 will then be centrally located with respect to a series of graduations 134 (Fig. 9) which are provided on the end face of the base structure 8! for each of the slidablestop members I66. By this arrangement the stop members 106 may then be accurately positioned by means of the graduations 134 to permit knurling of the piston to a predetermined distance on either side of the previously inscribed center line. If desired, a chart or table can be readily prepared which will indicate the number of graduations M4 to be employed in positioning each of the stop members I06 for any desired length of knurl track.

Although the invention has been described in detail with reference to certain preferred structural embodiments, it will be understood that various modifications and equivalent structures may be resorted to without departing from the 12 scope of the invention as defined in the appended claims.

I claim:

1. A device for knurling the thrust faces of the skirt portion of a piston, comprising a base, a movable knurl-carrying member mounted on said base, a knurling element carried by said knurlcarrying member and adapted to engage the exterior surface of the piston skirt, a manually operable driving means having driving engagement with said knurl-carrying member for actuating the latter whereby to operate the knurling element, said driving means including a manually operable member, a pair of ab-utments adjustably mounted on said base on opposite sides of one of said members in the path of movement thereof to limit the movement of the knurling element thereby to limit the length of the knurled band formed on the piston skirt, an anvil element mounted on said base in shiftable relation to said knurling element and adapted to engage the interior of the piston skirt, and means yieldingly urging said anvil element toward said knurling element.

2. A device for knurling the thrust faces of the skirt portion of a piston, comprising a base having a slideway therein, a knurl-carrying member slidably disposed in said slideway for reciprocating movement therein, a knurling element mounted on said knurl-carrying member and adapted to engage the exterior surface of the piston skirt, manual means for effecting reciprocating sliding movement of said knurl-carrying member within said slideway, an anvil member mounted on said base in shiftable relation to said knurling element and adapted to engage the interior surface of the piston skirt, and means for yieldingly urging said anvil member toward said knurling element.

3. A device for knurling the thrust faces of the skirt portion of a piston, comprising a base having a slideway therein, a knurl-carrying member slidably disposed in said slideway for reciprocating movement therein and having gear teeth thereon, a knurling element mounted on said knurl-carrying member and adapted to engage the exterior surface of the piston skirt, a drive shaft having a pinion mounted thereon in operative engagement with said gear teeth, manual means for rotating said drive shaft in alternate directions whereby to effect reciprocating sliding movement of said knurl-carrying member and said knurling element, an anvil member mounted on said base in shiftable relation to said knurling element and adapted to engage the interior surface of the piston skirt, and means for yieldingly urging said anvil member toward said knurling element.

4. A device for knurling the thrust faces of the skirt portion of a piston, comprising a work support for holding a piston during knurling and for stabilizing the piston during rotation thereof on its axis, and knurling mechanism comprising a manually'operable knurling element adapted to engage the exterior surface of the piston skirt and an anvil member adapted to engage the interior surface of the piston skirt, said anvil member be ing shiftably mounted relative to said knuriing element and being provided with means for yieldingly urging the same toward said knurling element, said work support comprising a pair of slidably .mounted semi-rigid wings adapted to engage the exterior of the piston at opposite sides thereof whereby to retain the piston against longitudinal twisting movement during knurling,

Said Wings being sufiiciently flexible to accommodate slight variations in diameter of the piston as the latter rotates on its axis between said wings and while the skirt portion thereof is clamped be tween said knurling element and said anvil member.

5. A device for knurling the thrust faces of the skirt portion of a piston, comprising a base, reciprocable knurling means movably mounted on said base and adapted to engage the exterior surface of the piston skirt, manually operable driving means for effecting reciprocation of said knurling means, an anvil member mounted on said base in shiftable relation to said knurling means and adapted to engage the interior surface of the piston skirt, pressure applying mechanism for yieldingly urging said anvil member toward said knurling means, and adjustable stop members engageable by one of said means for limiting the extent of reciprocating movement of said knurling means whereby to regulate the length of the knurl track on the piston skirt.

6. A device for knurling the thrust faces of the skirt portion of a piston, comprising a base, knurling means mounted for reciprocating sliding movement in a rectilinear path on said base and including a flat bar-type knurling element adapted to engage the exterior surface of the piston skirt, manually operable driving means having a driving connection with said knurling means for effecting said reciprocating sliding movement of said knurling means, an anvil member mounted on said base in shiftable relation to said knurling means and adapted to engage the interior surface of the piston skirt, means for yieldingly urging said anvil member toward said knurling means, and adjustable stop means coacting with opposite ends of said knurling means for regulating the extent of said reciprocating sliding movement.

'7. A device forknurling the thrust faces of the skirt portion of a piston, comprising a generally horizontal base, a knurling member mounted on said base and adapted to engage the exterior surface of the piston skirt, manual means for driving said knurling member, a bell crank pivotally mounted on said base and comprising a generally horizontal leg disposed above said base and a depending leg extending below said base, an elongated anvil-supporting arm secured to the horizontal leg of said bell crank and carrying an anvil member adapted to engage the interior surface of the piston skirt in substantial alignment with the knurling member, and a releasable spring loading mechanism extending generally horizontally through said base and coacting with the lower end of the depending leg of said bell crank for yieldingly urging said anvil member toward said knurling member under predetermined substantially constant pressure.

8. The device of claim 1 further characterized in that said knurl-carrying member comprises a knurl shaft journaled on said base, that said knurling element is in the form of a roller mount- Number 14 ed on said knurl shaft, and that said manually operable driving means has a geared connection with said knurl shaft for effecting rotary oscillating movement of said knurling roller.

9. The device of claim 1 further characterized in that said knurl-carrying member comprises a knurl shaft journaled on said base, that said knurling element is in the form of a roller mounted on said knurl shaft, that said knurl shaft is provided with gear teeth, and that said manually operable driving means comprises a drive shaft journaled in said base and having a gear sector mounted thereon in ,operative engagement with said gear teeth on said knurl shaft, and a hand lever secured to said drive shaft for effecting rotary oscillating movement of said knurling roller.

10. The device of claim 1 further characterized in that said knurl-carrying member comprises a knurl shaft journaled on said base, that said knurling element is in the form of a roller, that said manually operable driving means includes a hand lever for effecting rotary oscillating movement of said roller, and that said pair of abutments coact with said hand lever for limiting the extent of said rotary oscillating movement.

11. The device of claim 1 further characterized in that said anvil element is carried by an elongated anvil-supporting arm pivotally mounted on said base with said anvil element in substantial alignment with said knurling element, that said means yieldably urging said anvil element toward said knurling element comprises a releasable spring loading mechanism coacting between said base and said anvil-supporting arm for yieldingly urging said anvil element toward said knurling element under a predetermined sub stantially constant pressure, that spring means is provided for urging said anvil-supporting arm away from said knurling element when said spring loading mechanism is in released position, and that said mechanism comprises an elon gated member extending into said base, an adjustable helical spring encircling said elongated member, and a thrust member loosely carried on said elongated member for transmitting the pressure of said helical spring to said anvil-supporting arm.

CERNYW F. JONES.

References Cited in the file of this patent UNITED STATES PATENTS Name Date 1,373,095 Prossen Mar. 29, 1921 1,923,477 Coda Aug. 22, 1933 2,054,182 Unke Sept. 15, 1936 2,083,775 Carroll June 15, 1937 2,122,525 Huntsman July 5, 1938 2,153,863 Fall Apr. 11, 1939 2,190,963 Wheeler Feb. 20, 1940 2,312,225 Wilkinson Feb. 23, 1943 2,347,350 Jung et a1 Apr. 25, 1944 

